Mitt Romney never lets you see him sweat, but he is under some perspiration-inducing pressure as he prepares to step onto a debate stage Monday evening in Tampa.

Romney needs a forceful performance to regain the initiative after his double-digit drubbing in South Carolina at the hands of Newt Gingrich. But if the former governor gets too histrionic or too harsh, he will seem inauthentic, forfeiting the one quality—that of a steady, self-assured businessman—that has served him well.

We already know what Gingrich will do. Newt will be Newt, by turns forceful, hectoring and, by his own admission, grandiose, with a couple of condescending slaps at the NBC moderators thrown in just to protect the brand. Gingrich is a strong debater, agile enough even to turn a question about past marital infidelity into an applause line. Without the twin debates in South Carolina last week, he probably would have lost the primary.

The question now at the heart of this campaign: What’s Mitt got left?

Beyond the darts he throws Gingrich’s way, can Romney raise the level of his game in a way that forces Republican voters to reconsider him? Or is he a captive of his own limitations, a smart, seasoned, and awesomely uninspiring politician?

It would be a mistake for a media mob that has twice written off Gingrich—how dumb does that look now?—to overreact to the South Carolina results. The heavily evangelical and staunchly conservative electorate was tailor-made for the ex-Georgia congressman. Newt won’t have that advantage in the bigger and more diverse battleground of Florida, which votes Jan. 31. Mitt’s still got the money and the organization for the war of attrition ahead.

But NBC viewers on Monday will be looking at a candidate stripped of his aura of inevitability—a premise of electability that, it turns out, is central to his case for the nomination. He probably would love to skip the coming debates—the networks really control the calendar this year—but that would project a sense of panic.

Romney’s had a year to make the case to GOP voters and has fallen short. His vision of a presidential CEO appeals to the head but not the heart. Many Republican voters are mad—at President Obama, at the liberal establishment, at the media—and it is Gingrich who has skillfully channeled that anger. Newt comes armed for a knife fight, and Mitt shows up with a PowerPoint presentation. Can anyone imagine Romney calling a moderator’s question “despicable”?

Perhaps it is to Romney’s credit that he restrains his rhetoric, that he appeals to the sensible center where general elections are won. But candidates, especially primary candidates, need passion, and Romney seems a bit too calculating, even when it comes to so basic a question as releasing his tax returns. (He has a year to prepare for the question and then says “maybe”—seriously?) A more natural politician would use wit to brush off questions about his wealth; Romney’s responses seem forced and halting, his talk of pink-slip anxiety labored and ludicrous.

Undoubtedly, Romney will press Gingrich to release the details of his Freddie Mac non-lobbying contract, and papers from the House probe that led to his reprimand and $300,000 fine (though the 1,300-page ethics report is available online). But these jabs will seem like what they are, a transparent attempt to deflect attention from his own tax-return woes (Mr. 15 Percent says he’ll put out the 2010 return on Tuesday).

Romney offered a glimpse of this strategy against Gingrich on Sunday, saying in Florida that “at the end of four years it was proven he was a failed leader, and he had to resign in disgrace.”

The real challenge in the NBC faceoff, and a CNN debate later this week, is whether Romney can forge a connection with Republicans that goes beyond his Harvard pedigree and 59-point economic plan. Americans like a fighter, someone they can envision leading the charge in crisis situations, and Romney is afflicted with Dukakis disease, a competent technocrat in an era of anger.

He will, however, have one underappreciated advantage. Until now, Gingrich has been a protest candidate whose heated language rouses Republicans. On Monday night, though, the country will start looking at him as a potential president, someone who could grab the nomination and conceivably defeat Obama. As his advisers recognize, Newt still has to pass the commander-in-chief threshold, and he tends to be his own worst enemy when he’s riding high. The prospect of President Gingrich could make Romney look like a stable suitor—one who stays married after the excitement has worn off. The problem for Romney is that the party’s base remains worried about ideological infidelity.

Rick Santorum performed strongly in last week’s debates as well, but after weak showings in New Hampshire and South Carolina, his moment probably has passed. We are down to a two-man race in Florida, two contrasting characters who are selling very different versions of conservatism. Until Saturday, the overriding issue was whether Gingrich could emerge as the alternative to Romney. Now, for the first time, that question may be turned on its head.